|Musick, Jack - USDA-ARS RETIRED/DECEASED|
Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 2000
Publication Date: N/A
Interpretive Summary: On slowly-permeable clay soils, furrow irrigation water infiltration along the upper 2/3 of furrow length is usually adequate to wet the soil to about 4 feet deep as water moves along the furrow. However, the lower 1/3 of the irrigation furrow may not be adequately wetted unless a relative long irrigation time is used that causes water runoff loss from furrows ends. To address this concern, relatively deep tillage (12 inches) on the lower 1/3 of a furrow irrigated field was compared with conventional tillage (6 inches deep) on the Southern High Plains at Bushland, TX. Comparison was also made of blocked irrigation furrow ends (no water runoff) versus normal open-end furrows that received 4 to 6 more hours of irrigation and runoff. Deep tilling the lower 1/3 of the field increased irrigation infiltration by 10-15% during the first irrigation after tillage. However, subsequent furrow packing from tractor, planter and cultivator wheel traffic, along with soil settling from irrigation and rainfall during the corn crop growing season, all combined to reduce the intended deep tillage effect of increasing irrigation infiltration on the lower 1/3 of the field. Blocking furrow ends, to prevent runoff in combination with 4 to 6 hours less irrigation time, did reduce gross irrigation application up to 24% (5.2 inches over the entire field) while corn yield was only reduced by 13% (25 bu/ac) or less. Furrow blocking, with earlier irrigation shutoff that prevents runoff loss, can help furrow irrigators manage a limited water supply without having an excessive grain yield reduction. By this method, a valuable water resource can be conserved and irrigation pumping costs reduced.
Technical Abstract: Tillage methods between annual row crops on the Southern High Plains commonly include disking and chiseling or occasional deeper loosening (ripping) or moldboard plowing. On slowly permeable soils, irrigation infiltration on the upper 2/3 of furrow lengths is usually adequate to wet to about 1.2 m (4 ft). However, reduced infiltration time on the lower 1/3 3can reduce soil wetting and grain yield unless excessive furrow runoff is allowed. This study was conducted at Bushland, TX, to evaluate effects of ripping the lower 1/3 on infiltration, soil water distribution, and corn grain yield along the furrow. Rip treatments were tilled 0.3 m (12 in.) deep and the remainder of the field was chiseled 0.15 m (6 in.) deep. Four treatments included both blocked and open furrows with ripping and without ripping. Blocked-end furrows had irrigation shut off after 2 h ponding to allow water to reach furrow ends, whereas open furrows received 4 to 6 h more irrigation and runoff. Ripping the lower 1/3 increased infiltration by 10-15% after primary tillage, however, subsequent furrow traffic and soil consolidation from irrigation and rainfall reduced this effect on infiltration. Net irrigation, ET, and grain yield were not significantly affected. Furrow blocking with earlier irrigation shutoff did reduce gross irrigation by up to 24% while grain yield was only reduced 13% in 1995. In 1996, furrow blocking reduced irrigation by 11% and grain yield by only 3%.